For the purpose of endowing golf balls with better rebound, efforts have been made to ameliorate the formulation of polybutadiene used as the rubber base.
For example, JP-A 2000-313710 aims to develop a polymer having high thermal properties (e.g., thermal stability) and mechanical properties (e.g., tensile modulus and flexural modulus), and discloses a catalyst composition which enables to produce a conjugated diene polymer having a high content of cis-1,4 units in the micro-structure and a narrow molecular weight distribution. JP-A 2002-282393 and JP-A 2002-338737 describe solid golf balls having improved flight performance in which the solid core is formed mainly from a polybutadiene rubber obtained using the catalyst composition of JP-A 2000-313710.
For these golf balls, however, there is still left a room for further improvement in rebound and the property of molding and working.